The invention relates to a sensor for detecting the position of a movable part in a motor vehicle with a common drive for several position pickups and several path ranges according to German Utility Model Registration DE-GM No. 71 20 684. A step-variable resistor for use as a throttle flap position sensor is disclosed in DE-GM No. 71 20 684. It is essential in this arrangement that a housing on a single circuit board includes two electrically insulated potentiometer circuits and that each of these two circuits has a slider secured to a shaft of the variable resistor. This arrangement makes it possible to obtain two different characteristics over the entire range of the respective potentiometers, which characteristics are, in turn, suitable for different uses.
German Published Patent Application DE-OS No. 24 42 373 discloses an electrically controlled intermittently operating fuel injection arrangement having its injection signal generated on the basis of rotational speed and throttle flap position. In this arrangement, the throttle flap position is sensed by means of a potentiometer. With a view to accomplishing optimum metering of fuel, it is necessary to detect the throttle flap position very accurately in the range of relatively small opening angles of the throttle flap, that is, in the lower load range. Compared with higher load ranges, this requires a higher resolution in the lower load range.
It has been shown now that in some cases the detection of a potentiometer voltage using conventional 8-bit analog-to-digital converters is insufficient with respect to the relative resolution. In particular at small angles of opening, quantization effects a high surge per increment.
It is known to accomplish different resolutions using potentiometers having non-linear characteristics such as a logarithmic characteristic, for example. Large-scale production of such potentiometers is, however, problematical with respect to their exact reproducibility; moreover, the adjustment of such potentiometers in the motor vehicle causes accuracy problems.